Torsional damper

Abstract

A torsional damper for reducing the vibrations produced when a shaft is driven by the intermittent application of a discontinuous force thereto, e.g. the crankshaft of an internal combustion engine, comprising an integrally formed disk-like mass having three concentric zones, namely, an inner central zone, an outer annular zone, and an intermediate spring zone therebetween. The spring zone includes narrow, elongated, spirally-arranged, overlapping slots extending axially through the disk and radially between the inner and outer zones to provide spirally-arranged overlapping web portions which act as torsional springs or shock absorbers due to an inherent resiliency. The spirally slotted damper is formed as an integral unit by casting it from a metal such as cast iron with the spiraled slots having a predetermined size and shape to provide the desired damping effect.

I claim: 
     
       1. A torsional damper for damping out vibrations produced when a shaft is driven by the intermittent application of a discontinuous torque-like force comprising a unitary, integrally cast, disk-like mass having three concentric portions, namely, a first central portion adapted for engaging said driven shaft, a second outer annular ring portion, and an intermediate spring-like portion coupling said inner and outer portions, said spring-like portion including elongated, spirally-arranged, overlapping slots of uniform radial thickness extending axially through said disk and radially between said inner and outer portions to provide spirally-arranged integral web portions adapted to act as torsional shock-absorbing spring means for damping out said vibrations, and wherein for each spiral slot, its radial distances from the spiral center to any point along the web portion centerline is given by the equation r=r o  +αC. 
     
     
       2. The torsional damper of claim 1 further characterized in that said disk-like mass is a single, one-piece, integrally-cast piece of castable ferrous metal. 
     
     
       3. The torsional damper of claim 1 further characterized in that said at least three spiraled slots extend through a spiral angle of approximately 215°. 
     
     
       4. The torsional damper of claim 1 further characterized in that said outer annular ring portion is adapted to have its axial thickness varied during the forming process in order to obtain a predetermined specified polar moment of inertia for the overall damper. 
     
     
       5. The torsional damper of claim 1 further characterized in that the cross-sectional dimensions of said spirally-arranged web portions are constant along said radial spiral. 
     
     
       6. The torsional damper of claim 1 further characterized in that the cross-sectional dimensions of said spirally-arranged web portions may be varied to reinforce the more highly stressed areas so as to maintain the stress level constant over the length of the spiral web. 
     
     
       7. A torsional vibration damper apparatus for damping out rotational fluctuations produced when a crankshaft is driven by the discontinuous force applications of an internal combustion engine, said damper comprising a unitary, disk-like mass having a radially central portion adapted for engaging the crankshaft for rotation therewith, a concentric, radially outer annular portion, and an intermediate shock-absorbing portion connecting the inner portion to the outer portion, said intermediate portion including at least one spirally-arranged slot of uniform radial thickness extending axially through said intermediate portion and radially between said inner and outer portions, and wherein the centerline of the spiral web portion is defined by the equation r=r o  +αC, where r is the radial distance from the spiral center to any point on the web centerline, r o  is the initial radial distance from the spiral center to the centerline of the web portion at its radially innermost starting point, C is a constant which may be arbitrarily selected to determine a given radial distance increase per 360° of arc and α is the angle between the initial radial line r o  and the general radial line r, and a spirally-arranged web portion radially adjacent said spiral slot, said web portion being responsive to said discontinuous force application for yielding in a first radial direction to absorb the energy imparted to said shaft by said force application and store said energy as potential energy which is a function of the spring constant and displacement of said web portion thereby lessening the tendency of the rotational velocity of said shaft to increase during said force application and being responsive to the termination of said force application for returning in the opposite radial direction to its normal position for releasing the stored potential energy and converting it to kinetic energy thereby lessening the tendency of the rotational velocity of said shaft to decrease upon the termination of said force application so as to dampen out rotational fluctuations and produce a more uniform shaft rotation. 
     
     
       8. The torsional vibration damper of claim 7 further characterized in that said at least one spiral slot extends through a spiral angle of at least 180°. 
     
     
       9. The torsional vibration damper of claim 7 further characterized in that said intermediate portion includes a plurality of equally spaced, overlapping, spirally arranged slots, each of which is extends through a spiral angle of more than 180°.